Pretty much what everyone who used to use Zone-Alarm has done. It makes your computer safe, often by rendering the program trying to access the internet DOA. And then you accidentally set some system service up to be "more safe" and the OS itself starts to fall over dead. It's too intrusive, too much of a resource sink and in the end its wormed-in tendrils into the OS caused me to have to wipe and reinstall. Unfortunately there wasn't an analogous tool like Norton Removal Tool for Zone-Alarm.
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Fiasco LabsDec 11 '11 at 2:06

@FiascoLabs When I installed Comodo after disabling ZoneAlarm, I couldn't figure out why my internet wasn't working. After hours and hours, I finally figured it out: ZoneAlarm was disabled; I needed to uninstall it.
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Sicarius NoctisDec 11 '11 at 5:08

Yep, that's pretty much the case. No two anti-virus, anti-spyware or firewall packages can co-exist on any system anymore. You used to be able to have an active antivirus and a deactivated antivirus that you could run manually, but those days are long over. All these products have to become part of the operating system in order to intercept the malware, just some do a better job than others. And having two loaded at the same time means both are fighting for the same access to the OS. In its day, Zone-Alarm was a really good package.
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Fiasco LabsDec 11 '11 at 8:04